Optical Sensor Shielding Member for Leak Light Reduction
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Solution Overview
Problem
The existing electrophotographic image forming apparatuses face challenges in accurately measuring image density due to variations in sensitivity characteristics caused by leak light, which leads to high output offsets and large variations in detected values, hindering precise density correction and reducing image quality.
Innovation Solution
The apparatus incorporates a shielding member between the light emitting and receiving elements on a substrate to prevent leak light, and a controller adjusts the image forming conditions based on measurement data to correct for leak light effects, ensuring accurate image density measurement and correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the light emitting element and light receiving element are directly mounted on the substrate surface for surface mounting, then the optical sensor can be downsized and reduced in cost, but irradiation light from the light emitting element propagates on the substrate surface and reaches the light receiving element, causing leak light that increases individual differences in sensitivity characteristics
Solution Approach 1:
A resin layer is introduced as an intermediary medium between the light emitting element and light receiving element on the substrate surface. This resin layer has light scattering properties that prevent direct propagation of irradiation light while allowing the surface mounting structure to be maintained, thus eliminating leak light without compromising manufacturing ease
Solution Approach 2:
A thin resin film or coating is applied over the light emitting element and light receiving element on the substrate surface. This thin film structure scatters the light path and prevents direct light transmission while maintaining the compact surface-mounted configuration, thereby reducing individual differences in sensitivity characteristics
2Reliability
If the driving current of the light emitting element is increased to suppress the effect of toner soil, then the detected value can be maintained within the predetermined range, but the amount of leak light is increased, causing the optical sensor to change in sensitivity characteristics
Solution Approach 1:
The resin layer with light scattering properties converts the harmful leak light into a beneficial diffuse light distribution. By scattering the light before it reaches the light receiving element, the system can use higher driving currents to overcome toner soil effects without the negative impact of concentrated leak light, thus improving reliability while maintaining measurement precision
Solution Approach 2:
The introduction of the resin layer changes the optical parameters of the system by adding light scattering capability. This allows the driving current of the light emitting element to be optimized independently from the leak light problem, enabling higher currents to be used for better toner soil compensation without causing sensitivity characteristic changes
3Reliability
If the output gain of the light receiving element is increased to suppress the effect of toner soil, then the detected value can be maintained within the predetermined range, but the amount of leak light is increased, causing the optical sensor to change in sensitivity characteristics
Solution Approach 1:
The resin layer converts the harmful leak light into scattered diffuse light, allowing higher output gain to be applied to the light receiving element without amplifying concentrated leak light signals. This enables better suppression of toner soil effects while maintaining stable sensitivity characteristics and measurement precision
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables precise measurement and correction of image density, reducing the impact of leak light on sensitivity characteristics, thereby improving the accuracy and quality of the images formed by the image forming apparatus.
Implementation Method 1
an optical sensor including a light emitting element and a light receiving element
Implementation Method 2
an amount of reflected light from the image bearing member is changed
Implementation Method 3
a shielding member, which is provided between the light emitting element and the light receiving element on the substrate
Data Source
AI summary
Provided is an image forming apparatus configured to detect an image density while suppressing a change in sensitivity characteristic of an optical sensor, which is caused by leak light. The image forming apparatus includes the optical sensor configured to measure a measurement image formed on an intermediate transfer belt, and output a detected analog value indicating a measurement result, and a controller. The optical sensor includes a light emitting element and a light receiving element. The controller includes a memory configured to store profile data regarding a driving current of the light emitting element and an amount of leak light directly received by the light receiving element from the light emitting element. The controller is configured to detect the amount of leak light corresponding to the driving current of the light emitting element at a time of measurement of the measurement image based on the profile data.